Prior attempts at corrosion monitoring used manual instrumentation to measure resistance changes at each site. This instrumentation had to be manually balanced in order to achieve the sensitivity necessary to detect small resistance changes. Although such conventional techniques are relatively satisfactory where there is adequate space and time for their use, there are many corrosive environments that need continuous or frequent corrosion monitoring and/or are relatively inaccessible making it difficult or impossible to use conventional techniques.
With aging fleets of aircraft in use both in the military and commercial sectors, corrosion of body and support component surfaces in secluded areas is of crucial concern. Current efforts to detect corrosion on aircraft surfaces consist of visual inspection of the accessible surfaces on a routine basis. Aircraft surfaces that are difficult to access often receive less attention and may not be inspected until aircraft overhaul, which typically occurs every five years. The overhaul process involves the disassembly of the body of the aircraft. The body panels are removed and inspected leaving only a frame skeleton. This process has often revealed corrosion problems in many of the remote areas of the dismantled aircraft. Potential safety concerns prompt the need for continuous corrosion detection capabilities in secluded aircraft compartments.